I was trying to use the script 'dvd2usb.sh' as described on the DVD (and in the magazine). The idea is to make an existing ISO file (not located on the DVD, but on my HD) to an IMG file, and then copy it over to a USB stick.
When trying to execute the script nothing happens; and I don't get any error messages. If I try to click on the file icon from the GUI a windows appears but closes down again, in a fraction of a second....as if it tried to start but didn't managed.
I'm using Mint 12, 64 bit.

That script is only for converting the LXFDVD on which it resides to a USB-bootable image. If you want to make an existing ISO image USB-bootable, you need the isohybrid program from the syslinux package. Install syslinux and then run

That's a warning, not an error. It is not stating that the procedure failed, only that some older BIOSes cannot boot from such a device. Since this depends on the computer and not the ISO file, the only way to test it is to dd the file to a USB device an try it.

AFAIK the Gentoo discs are already hybrids, but running isohybrid again shouldn't do any harm.

"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)